Characterization of a canine model of glycogen storage disease type IIIa

Abstract

SUMMARYGlycogen storage disease type IIIa (GSD IIIa) is an autosomal recessive disease caused by deficiency of glycogen debranching enzyme (GDE) in liver and muscle. The disorder is clinically heterogeneous and progressive, and there is no effective treatment. Previously, a naturally occurring dog model for this condition was identified in curly-coated retrievers (CCR). The affected dogs carry a frame-shift mutation in the GDE gene and have no detectable GDE activity in liver and muscle. We characterized in detail the disease expression and progression in eight dogs from age 2 to 16 months. Monthly blood biochemistry revealed elevated and gradually increasing serum alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP) activities; serum creatine phosphokinase (CPK) activity exceeded normal range after 12 months. Analysis of tissue biopsy specimens at 4, 12 and 16 months revealed abnormally high glycogen contents in liver and muscle of all dogs. Fasting liver glycogen content increased from 4 months to 12 months, but dropped at 16 months possibly caused by extended fibrosis; muscle glycogen content continually increased with age. Light microscopy revealed significant glycogen accumulation in hepatocytes at all ages. Liver histology showed progressive, age-related fibrosis. In muscle, scattered cytoplasmic glycogen deposits were present in most cells at 4 months, but large, lake-like accumulation developed by 12 and 16 months. Disruption of the contractile apparatus and fraying of myofibrils was observed in muscle at 12 and 16 months by electron microscopy. In conclusion, the CCR dogs are an accurate model of GSD IIIa that will improve our understanding of the disease progression and allow opportunities to investigate treatment interventions.

Alglucosidase alfa enzyme replacement therapy as a therapeutic approach for glycogen storage disease type III

“…This treatment could also be beneficial for patients with other GSDs. In future studies, we will test the efficacy of rhGAA treatment in a canine model of GSD IIIa [16].…”

Antibody-mediated enzyme replacement therapy targeting both lysosomal and cytoplasmic glycogen in Pompe disease

“…Periodic acid-Schiff (PAS) staining was done at Duke Pathology Laboratory as described previously [25].…”

A Modified Enzymatic Method for Measurement of Glycogen Content in Glycogen Storage Disease Type IV

“…Muscle tissues were obtained from 3-month-old GAA knockout (GSD II) mice (Raben et al 1998) and from 4-month-old GSD IIIa dogs (Yi et al 2012). GSD IV (Gbe1 ys/ ys ) mice (Akman et al 2015) were euthanized at age of 3 months following overnight fasting for collection of tissues.…”

“…Muscle tissues from 3-month-old wild-type (C57BL/6) mice were used as controls. Fresh tissues were fixed in 10% neutral buffered formalin for PAS staining or frozen in À80 C freezer until use (Yi et al 2012). All animal experiments were approved by the Institutional Animal Care & Use Committee at Duke University and were in accordance with the National Institutes of Health guidelines.…”

“…An enzymatic method based on homogenization of tissues in cold water followed by Aspergillus niger amyloglucosidase (EC 3.2.1.3) digestion has become widely used for measuring glycogen content in tissue (Huijing 1970;Van Hove et al 1996;Kikuchi et al 1998;Raben et al 2003). In the past decade, our team has had success using this method to quantify glycogen in various tissues from experimental animals with GSD type I, II, or III (Sun et al 2005(Sun et al , 2007Koeberl et al 2006;Yi et al 2012Yi et al , 2014. Recently, in our work with a mouse model of GSD IV, we found that the measured tissue glycogen contents were at extremely low levels, which contradicts with the observation that strongly PAS-positive PB were present in these tissues.…”